1. Field of the Invention
The invention relates generally to a system for continuously mining coal underground and, more particularly, to such a system having a substantially automatic sequential control for a continuous miner, a combination articulated haulage/tramming conveyor and a roof bolting machine therebetween.
2. Description of the Prior Art
Coal is typically found in substantially horizontal seams extending through rock strata such as limestone, sandstone or shale. Surface mining and underground mining are the primary methods used to mine coal. Surface mining may be strip mining which involves the removal of the overburden by means of a drag line or other earth moving equipment to fully expose the coal seam for recovery. However, strip mining is limited by the depth of the overburden, which eventually makes strip mining impractical. When the depth of the overburden makes strip mining impractical, a large quantity of coal may remain in a seam. Recovery of this coal is accomplished by highwall mining wherein an entry or a hole is initiated at the exposed face of the seam at the highwall, and mining follows the seam inwardly from the highwall. A method and apparatus of mining a highwall are disclosed in U.S. Pat. Nos. 5,364,171; 5,232,269; 5,261,729 and 5,112,111, respectively entitled "Apparatus and Method for Continuous Mining"; "Launch Vehicle for Continuous Mining Apparatus"; "Apparatus for Continuous Mining"; and "Apparatus and Method for Continuous Mining", which are owned by Mining Technologies, Inc. Early highwall mining technology included mobile conveyors such as disclosed in U.S. Pat. No. 4,957,405, entitled "Apparatus for Mining". A control for a continuous miner and a trailing conveyor which may be used in highwall mining is disclosed in U.S. Pat. No. 5,185,935, entitled "Method and Apparatus for Separation Measurement and Alignment System". A combination haulage and tramming conveyor is disclosed in United Kingdom Patent No. 1,373,170, entitled "Plate Conveyor".
When a coal seam is sufficiently deep, underground mining is utilized which often requires a bolter car to insert roof bolts to provide a stable roof above the workers.